It depends whether the cafe is short of customers or crowded.
In the first case the cafe owner would be grateful and in the second case resentful.

An empty cafe looks dismal and shy people prefer not to enter it and sit there alone.
Half-empty is perfect for those who want to discuss something or restaure themselves on their own.
A crowded one is preferred by some. Also by pick pocketers, by the way.

If a customer takes away space and air the waiteress can come and give him a dirty look.
They have their ways of making a person feel uneasy and leave, I am sure.

Above us only sky wrote:If someone in a cafe for a whole afternoon yet only ordered one cup of drink, then is that person evil?

It depends what this someone did in the morning, for example, did it just shoot a classroom full of schoolchildren?

If so you could almost claim the individual is evil, unless the cafe is Starbucks and the individual still has enough amo to finish a cafe full of pretentious fuckwits that have no understanding of what makes a good coffee.

Above us only sky wrote:If someone in a cafe for a whole afternoon yet only ordered one cup of drink, then is that person evil?

Just think about it. Does it seem it is evil? The answer is quite clearly a no. So then what is it? It is not wickedness either. It is vices showing in the person. Vices are like - greed, gluttony, anger, ego, envy, laziness, lust and so on. Another example of vices showing up in a person is - did not intend to cheat the grocer when he/she charged less by mistake, but kept the extra anyways and did not mention it. A plan to cheat, and without reason, would be wickedness. A more gruesome plan would be evil showing.
P.S. This is assuming person in the cafe was not awaiting someone, or was there for so long unwelcomed. Like, we could just go to a cafe, take our computer with us, and be there for some while, I think it should be fine, 'cause people like doing that, and there's nothing wrong in it. But if we are not welcome, then we must leave soon, or order more stuff.